1. Field of the Invention
The present invention relates to a microelectromechanical integrated sensor structure having a rotary driving motion. In particular, in the following description reference will be made to a gyroscope (whether uniaxial, biaxial, or triaxial), which can possibly operate as an accelerometer (whether uniaxial, biaxial, or triaxial).
2. Description of the Related Art
As is known, microprocessing techniques enable formation of microelectromechanical structures or systems (the so-called MEMS) within layers of semiconductor material, which have been deposited (for example, in the case of a layer of polycrystalline silicon) or grown (for example, in the case of an epitaxial layer) on top of sacrificial layers, which are removed by chemical etching. Inertial sensors, accelerometers and gyroscopes obtained with said technology are encountering an increasing success, for example in the automotive field, in inertial navigation, or in the sector of portable devices.
In particular, integrated semiconductor gyroscopes are known, which are made with MEMS technology. Said gyroscopes operate according to the theorem of relative accelerations, exploiting Coriolis acceleration. When an angular velocity is imparted on a movable mass that is moving with a linear velocity, the movable mass “feels” an apparent force, referred to as Coriolis force, which determines a displacement thereof in a direction perpendicular to the direction of the linear velocity and to the axis of rotation. The movable mass is supported via springs that enable a displacement thereof in the direction of the apparent force. According to Hooke's law, said displacement is proportional to the apparent force, and consequently, from the displacement of the movable mass, it is possible to detect the Coriolis force and the angular velocity that has generated it. The displacement of the movable mass can, for example, be detected capacitively, by measuring, in resonance conditions, the variations in capacitance caused by the movement of movable electrodes, integrally fixed to the movable mass and comb-fingered to fixed electrodes.
Examples of embodiment of integrated gyroscopes of a MEMS type are described in EP-A-1 253 399 and EP-A-1 365 211, filed in the name of the present applicant, which relate to gyroscopes with a rectilinear driving motion, or else in WO 02/103364 and U.S. Pat. No. 6,062,082, which relate to gyroscopes with rotary driving motion.
In general, gyroscopes of a known type are not completely satisfactory for what concerns simplicity of production, reduction in dimensions, efficiency, and immunity to disturbance. In addition, microelectromechanical structures of a known type enable a limited configurability. Furthermore, rejection of external interference (for example, due to spurious linear or angular accelerations) is critical.